Java Stream API
Java 8引入了Stream的概念，掌握这个概念的最佳方式是阅读Java官方文档。
可以浏览一下Oracle Java文档或是Android官方文档。
有些关键的概念需要掌握：stream、source、stream pipeline、stream operations、intermediate operations、terminal operation。
/**
* Returns a sequential {@code Stream} with this collection as its source.
*
* <p>This method should be overridden when the {@link #spliterator()}
* method cannot return a spliterator that is {@code IMMUTABLE},
* {@code CONCURRENT}, or <em>late-binding</em>. (See {@link #spliterator()}
* for details.)
*
* @implSpec
* The default implementation creates a sequential {@code Stream} from the
* collection's {@code Spliterator}.
*
* @return a sequential {@code Stream} over the elements in this collection
* @since 1.8
*/
default Stream<E> stream() {
return StreamSupport.stream(spliterator(), false);
}
Stream实例只能被使用一次，否则会抛出Runtime Exception：
java.lang.IllegalStateException: stream has already been operated upon or closed
The right and most convenient way to use streams are by a stream pipeline, which is a chain of stream source, intermediate operations, and a terminal operation.
将Stream转换为int、long或double流
abstract DoubleStream mapToDouble(ToDoubleFunction<? super T> mapper)
abstract IntStream mapToInt(ToIntFunction<? super T> mapper)
abstract LongStream mapToLong(ToLongFunction<? super T> mapper)
allMatch，anyMatch和noneMatch方法
abstract boolean allMatch(Predicate<? super T> predicate)
abstract boolean anyMatch(Predicate<? super T> predicate)
abstract boolean noneMatch(Predicate<? super T> predicate)
June 6, 2018 ∙
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